Hair and Scalp Properties

Question 1

Trichology

Answer 1

the study of hair, including its diseases and care

Question 2

hair root

Answer 2

part of the hair located below the surface of the epidermis

Question 3

hair shaft

Answer 3

part of the hair that projects above the epidermis

Question 4

hair follicle

Answer 4

tube-like structure in the skin or scalp that surrounds the hair root and anchors the hair in the skin

Question 5

hair bulb

Answer 5

found at base of the follicle; has a bulb shape and contains living cells that will form the hair strand

Question 6

dermal papilla

Answer 6

cone-shaped elevation found at the base of the bulb

Question 7

keratinization

Answer 7

process by which newly formed cells in the hair bulb mature, fill with keratin, move upward, lose their nucleus, and die

Question 8

What % of hair is protein?

Answer 8

90%

Question 9

COHNS elements

Answer 9

five elements—carbon, oxygen, hydrogen, nitrogen, and sulfur—that make up human hair, skin, tissue, and nails

Question 10

Amino acids

Answer 10

form the building blocks of protein; link together end to end like pop beads by strong, chemical peptide bonds (end bonds) to form the polypeptide chains that comprise proteins

Question 11

peptide bonds

Answer 11

also known as an end bond; chemical bond that joins amino acids to each other, end-to-end, to form a polypeptide chain

Question 12

polypeptide chain

Answer 12

long chain of amino acids linked by peptide bonds

Question 13

side bonds

Answer 13

bonds that cross-link polypeptide chains and are responsible for the extreme strength and elasticity of human hair; account for about one-third of hair’s overall strength

Question 14

hydrogen bond

Answer 14

a weak physical side bond. The attraction of opposite charges forms hydrogen bonds. They are easily broken by water or heat, such as during wet and thermal styling. When the hair dries or cools, the bonds reform.

Question 15

salt bond

Answer 15

a weak physical side bond. Salt bonds, like hydrogen bonds, result from attracting opposite charges. Salt bonds are broken by changes in pH, so they are easily broken by strong alkaline or acidic solutions.

Question 16

disulfide bond

Answer 16

strong chemical side bond that joins the sulfur atoms of two neighboring cysteine amino acids to create one cysteine, which joins together two polypeptide strands like rungs on a ladder. Permanent waves and hair relaxers alter disulfide bonds.

Question 17

cysteine

Answer 17

amino acid with a sulfur (S) atom that joins together two peptide strands

Question 18

lanthionine bonds

Answer 18

bonds created when disulfide bonds are broken by hydroxide chemical hair relaxers

Question 19

Average hair density

Answer 19

approximately 2,200 hairs per square inch, with a total of about 100,000 hairs on the scalp. Density varies with natural hair color; blondes usually have the highest density, while redheads tend to have the lowest density.

Question 20

How far will hair stretch?

Answer 20

Wet hair with average elasticity will stretch between 30 to 50 percent of its length and return to that same length without breaking. Dry hair stretches about 20 percent of its length.

Question 21

Lanugo hair

Answer 21

short, fine hair that covers a fetus and generally sheds within a few weeks of birth.

Question 22

Vellus hair

Answer 22

short, fine, unpigmented hair that appears on the body, often referred to as peach fuzz. It is typically less than one-third inch long (approximately 1 cm) and can appear anywhere on the skin apart from the palms, soles, and lips

Question 23

Terminal hair

Answer 23

long pigmented hair on the scalp and body. It is coarser than vellus hair and, except for gray hair, it is pigmented. It may have a medulla.

Question 24

anagen phase

Answer 24

also known as the growth phase; hair phase during which new hair is produced

Question 25

catagen phase

Answer 25

brief transition period between the growth and resting phases of a hair follicle; signals the end of the growth phase: lasts one to two weeks.